The present invention relates to a revolution counts detection apparatus for detecting the revolution counts.
FIG. 5 shows the conventional apparatus for detecting the revolution counts of an electric motor.
In a revolution counts detection apparatus 50 for detecting the revolution counts of an electric motor M, a pulse generator 51 generates, as an output thereof, a pulse signal corresponding to revolution of the electric motor M. A digital counter 52 counts the number of pulses of the pulse signal produced from the pulse generator 51 so as to obtain the number of revolutions.
In the case of performing control such as positional control or the like by using the revolution counts obtained by the revolution counts detection apparatus 50, the revolution counts is converted into an analog signal again by using a D/A converter.
In the foregoing conventional revolution counts detection apparatus, there has been a problem in that since signal conversion is once performed into a digital signal to thereby obtain the revolution counts, the apparatus configuration is complicated to make the cost high.
Further, in order to use the output signal of the revolution counts detection apparatus to perform control, caused is a new problem in that it becomes necessary to use a D/A converter for converting into an analog signal again to make the cost higher.